Objective:

The objective of this research project is to
calculate stratospheric descent rates at various times and locations in the
Southern Hemisphere using
several temperature, water vapor, and ozone data sets and a radiative transfer
model.

Approach:

The descent rate within the polar vortex using several
radiative transfer models and newly acquired data sets has been investigated.
The primary
radiative transfer model used is the NCAR CCM2 general circulation model
radiation code. A more accurate, but computationally expensive, model called
MODTRAN
also was used for sensitivity tests and comparisons. Three data sets have
been used in the cooling rate calculation. The first data set consists of 1994
temperature
retrievals from the airborne (High Resolution Interferometer Sounder) instrument
in the antarctic polar vortex. These profiles extend from the surface to
the aircraft altitude in the lower stratosphere. They are valuable as an independent
comparison with data sets used in previous studies of the descent rate. Data
from numerical weather prediction model analyses comprise the second data
set.
The United Kingdom Meteorological Office (UKMO) analyses are primarily used
in this study because of the model’s emphasis on the middle atmosphere.
The final data set contains balloon soundings at McMurdo Station, Antarctica.
Descent rates have been calculated from these data sets, and comparisons
to the UKMO analyses have been made. Results of clear sky calculations, as
is typical of previous studies, show lower descent rates.

Progress and Final Reports:

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.